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For your ears only

By Barry Fox

WHEN you’re crawling along in heavy traffic, what you want to know is how
long you’ll have to wait before the congestion clears. What you are more likely
to get is news of other hold-ups miles away. But now the European Broadcasting
Union (EBU) has devised a system that delivers up-to-the-minute traffic news
targeted to each driver’s location. The BBC’s research laboratory at Kingswood
Warren in Surrey has just started trials of the system.

Like most broadcasters, the BBC collects traffic news from the police, travel
organisations and local authorities. This is relayed to the broadcasting
studios, where presenters select the incidents they think will interest their
listeners most. On national radio stations, this means that drivers in Scotland,
for example, have to listen to news about hold-ups hundreds of miles away in
London.

The BBC already has a system that goes some way to filtering information for
a particular locality. Known as the Radio Data System (RDS), it transmits a
digital switching signal along with the conventional analogue radio signal. The
digital signal automatically retunes a car’s radio to a local station when there
is a traffic news flash. But even local stations can cover a wide area, so each
traffic message is still likely to be relevant to only a few listeners.

Attempts to automate the system, by adding a digital messaging channel, have
foundered because the RDS data channel carries only a meagre 37 bits per second.
Messages therefore have to be transmitted in coded form, which receivers convert
into traffic messages that specify road numbers and locations. For this they
need the help of information contained on a smart card or CD-ROM. But this
information quickly goes out of date as new roads are built.

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Europe’s Digital Audio Broadcasting (DAB) system, which has also been adopted
by Canada, can carry traffic information at a rate of 8 kilobits per second, on
top of the 1.5 megabits per second used for programmes. This can deliver full
details of all Britain’s travel news in a few seconds, which the receiver stores
and then sifts through to find relevant local items. These messages can be
delivered on a head-up visual display or by synthesised voice.

A scheme devised by the Transport Protocol Experts Group (TPEG) of the EBU,
chaired by BBC engineer Simon Parnall, allows information to be made much more
local than is possible with RDS. In a simple receiver, a passenger would have to
key in the car’s location. But it will also be possible to combine a TPEG radio
with a GPS satellite navigation receiver to fix its location automatically. This
flexibility is possible because TPEG defines locations by latitude and longitude
as well as giving road names and numbers. The TPEG information can also be used
to generate graphics on a computer or digital TV set.

As part of the trials, the BBC is transmitting all its traffic data with the
DAB radio broadcasts that now reach 60 per cent of Britain’s population. It is
also putting the raw TPEG-format data on the Internet, where it can be used for
the testing of prototype TPEG receivers.

Meanwhile, the world’s first digital radio tuner intended for home use went
on the market this week. The £800 device, made by Arcam of Britain, plugs
into any hi-fi stereo amplifier and gives near CD-quality sound.